In general, the thickness of the placenta at 18 weeks of pregnancy is about 1.6 cm. It is not good for the growth of the fetus if the placenta is too thick or too thin during pregnancy. The placenta is an important organ for the exchange of materials between the fetus and the mother, and as the months of pregnancy increase, the placenta will generally thicken and increase in size, rather than gradually become thinner and smaller. In general, the thickness of full-term placenta is between 2.5 centimeters and 3.8 centimeters, and the thickest will not exceed 5 centimeters. Therefore, pregnant women must do the appropriate obstetric examination on time, if the thickness of the placenta is within the normal range, there is no need to worry about it. In the late pregnancy, it is necessary to test the placenta level regularly, and pay attention to whether the placenta has matured prematurely and calcification occurs. Whether the placenta is too thick or too thin is not normal. If the placenta is too thick in late pregnancy, first of all, we should exclude pathological conditions, generally, the placenta is too thick and easy to mature prematurely, resulting in fetal hypoxia in the uterus; if the placenta is too thin, it will reduce the function of the placenta in supplying nutrients and oxygen, resulting in delayed development of the fetus. In serious cases, it can also cause chronic fetal hypoxia. Therefore, it is recommended that pregnant women should have regular checkups, pay attention to fetal movement, and terminate the pregnancy as soon as possible if necessary.